June 20 (Bloomberg) -- A week of auctions start in London today, with as much as 200 million pounds ($366 million) of paintings by Amedeo Modigliani, Lucian Freud, Francis Bacon and others on the block.

The sales begin just as the No.1 art fair closes in Basel, Switzerland. They may show that prices for some fashionable 21st- century artists have peaked as buyers use up their art budgets or favor more established names.

``Younger art was making all the noise,'' says Fernando Mignoni, who runs Christie's International's contemporary department in London. ``Now, there's a bit of a shift to postwar art. At these price levels, collectors are becoming more conservative.''

Some works by Maurizio Cattelan and Marlene Dumas didn't sell at New York's May auctions, or took less than expected. Pricing of two Dumas paintings is back to pre-February levels for Christie's June 23 contemporary sale, Mignoni says, and, ``We are going to reassess how to estimate Cattelan.''

Tonight, Sotheby's Holdings Inc. holds its first impressionist and modern sale; Christie's turn is tomorrow. Contemporary auctions, which get more attention as younger buyers enter the market, start on June 22, except for Bonhams, which sells contemporary art this afternoon.

U.K. painter Freud's new popularity will be tested. Six of his paintings are on the block at the evening sales as owners try to profit from rising prices.

``Ideally, you don't want that much in the same week,'' says Christie's Mignoni.

Portrait of Bella

He values ``Bella,'' a portrait of Freud's naked daughter, at as much as 2.2 million pounds. It shows her in 1983 at age 21, lying stiffly on a sofa, her face averted and an arm across her waist. The seller is James Kirkham, Freud's former London dealer.

London-based Christie's put the top estimate for ``Bella'' below its low estimate for Freud's ``Naked Portrait'' of model Kate Moss, which fetched 3.9 million pounds in February -- a record for a Freud nude.

Sotheby's put a top estimate of 3 million pounds on ``Man With a Feather,'' a surreal 1943 Freud self-portrait with squared outlines that shows the artist standing with a feather in front of a London house.

Fifty-eight collectors called after getting Sotheby's brochure on the picture, says Cheyenne Westphal, who heads New York-based Sotheby's contemporary group in Europe. Freud and Bacon have become completely international in their appeal, she says, making them more akin to Jackson Pollock, Gerhard Richter and Andy Warhol.

Some of the fevered buying that was seen at Art Basel may carry over to London, collectors say.

``I'm bidding on five lots, but will not match the frenzy,'' says Ali Bagherzadeh, a London-based manufacturing executive and collector of contemporary art.

Currency Factor

More U.S. collectors than usual are selling art in London. ``If an American sells a painting priced in pounds, he gets more dollars in translating'' the pounds back into the U.S. currency, says Olivier Camu, an international director of Christie's impressionist and modern department in London.

A raft of works -- by Freud, Pierre-August Renoir, Lyonel Feininger, Nicolas de Stael, Cy Twombly, Jean-Michel Basquiat and Bridget Riley -- are being sold by owners who bought them in the 1990s.

At Sotheby's, Sean Connery is offering a map-like De Stael painting valued at as much as 600,000 pounds; New York's Museum of Modern Art is selling a 1892 painting by Henri Edmond Cross to raise money for new works. ``Vendanges,'' or the grape harvest, was a 1998 gift from Mrs. John Hay Whitney and has a top value of 1.8 million pounds.

Bacon Work

The sellers of Bacon's ape-like 1967 ``Portrait of George Dyer Staring into a Mirror'' are heirs of a U.S. collector who bought the picture in 1995, Mignoni says. It cost $1.4 million, says sales tracker Artnet AG. Christie's has a top value of 3.5 million pounds on the Dyer double portrait now, making it the priciest contemporary work of the week.

Heirs of Paris collector Jonas Netter are offering Modigliani's 1919 head and shoulders ``Portrait de Jeanne Hebuterne'' for as much as 2 million pounds through Christie's. A more complete painting of Modigliani's lover drew crowds at Art Basel last week.

``If I had the choice and the money, I would buy the whole Jeanne,'' said Paris gallery owner Olivier Malingue, who was asking 11 million euros ($13.5 million) for the portrait at his booth.

Heirs of France's Friedmann family are selling three Degas works at Sotheby's. ``Danseuses Rajustant Leur Coiffure,'' a pastel depicting two ballerinas fixing their hair, was bought in 1937. The top value is 1.8 million pounds.

In May, 30 percent of Sotheby's impressionist and modern pictures didn't sell. Estimates were high because sellers wanted to break even, says Philip Hook, a senior Sotheby's director in the London impressionist and modern department. It's easier to price art realistically if it wasn't bought in the boom, he says.

Beuys by Warhol

The Warhol of the week is a 1981 portrait of artist Joseph Beuys in his trademark hat, offered by a French collector and valued by Christie's at as much as 1.8 million pounds. Done in blues and reds from a photographic negative, it's dusted with ground glass.

Sotheby's has a large spot painting by Damien Hirst, who just had a show at New York's Gagosian Gallery. Hirst painted the 204-inch-long work (518 centimeters) in 1998 for Amy Sacco's Lot 61 Restaurant in New York, says the Web site of art adviser Yvonne Force, who chose art for the restaurant.

The top estimate is 400,000 pounds. That's as much as a Mark Rothko and other classic 20th-century works being offered this week.

A top-priced impressionist and modern lot is Kees van Dongen's 1906 ``Femme au Grand Chapeau,'' a bare-breasted woman wearing a hat. For tonight's sale, Sotheby's values it at as much as 4 million pounds.

Van Dongen's simple shapes and bright colors appeal to newly rich collectors, says Hook. The picture was auctioned in 1997 for 2.2 million pounds, says Artnet. Van Dongen's auction record, set last year by Christie's New York for ``Femme Fatale,'' is $5.9 million, or around 3.2 million pounds.